Torsional ultrasound hand piece that eliminates chatter

Abstract

A torsional ultrasound surgical hand piece lessens or eliminates chatter from lens material by imparting a twisting, rotary motion to a tip of a phacoemulsification needle at a resonant frequency in excess of 32 kHz. The hand piece has a horn that is designed to operate at an elevated frequency while maintaining size constraints for hand-held ophthalmic instruments. Optionally, heat generation is reduced either through the use of a polyimide tubing situated between the needle and the infusion sleeve, through the use of thermal watch to prevent overheating at the incision, and/or through the use of a bypass hole in the needle that diverts flow under suction into the needle via the bypass hole instead of exiting through an irrigation opening in the infusion sleeve when a tip port is occluded by lens material.

What is claimed is: 
     
       1. An ophthalmic ultrasound surgical instrument, comprising:
 a surgical hand piece suited for phacoemulsification that includes a phacoemulsification needle that is hollow to define an aspiration passage and that distally terminates at a tip with a tip port, the needle being bent or angled; 
 an infusion sleeve arranged radially outside of the needle so as to define therebetween an irrigation passage to channel irrigation flow, the infusion sleeve defining an irrigation opening arranged for the irrigation flow to exit the irrigation passage; 
 a heat generation reduction structure configured to reduce heat present at the needle, wherein the heat generation reduction structure includes a bypass hole in the phacoemulsification needle, the bypass hole being configured to divert the irrigation flow from the irrigation passage to enter the aspiration passage under suction via the bypass hole while the port is obstructed and thereby prevent the irrigation flow from otherwise exiting through the irrigation opening; 
 a horn with a distal section and a resonant section, the distal section being longer than the resonant section, the distal section and the resonant section each having a generally cylindrical shape, the distal section having a cross sectional area that is less than the cross sectional area of the resonant section, the horn coupled to the needle; and 
 a driver configured to impart a twisting, rotative movement to the tip at an elevated resonant frequency sufficient to eliminate chatter otherwise present at lower resonant frequencies. 
 
     
     
       2. The instrument of  claim 1  further comprising a controller of the driver that directs the driver to alter an amount, duration or type of ultrasound power imparted to the tip of the phacoemulsification needle based on an analysis that tracks a history of the ultrasound power over time and its effect on changing temperature. 
     
     
       3. The instrument of  claim 1  further comprising a controller of the driver that directs the driver to introduce pauses in the twisting, rotative movement. 
     
     
       4. The instrument of  claim 1  further comprising a controller of the driver that directs the driver to vary an amplitude of the ultrasound power being applied. 
     
     
       5. The instrument of  claim 1 , wherein the driver is configured to impart the twisting, rotative movement to the tip at a resonant frequency of at least 40 kHz. 
     
     
       6. The instrument of  claim 1 , further comprising a controller of the driver that directs the driver to vary a duty cycle of the ultrasound power being applied. 
     
     
       7. The instrument of  claim 1 , further comprising a controller that tracks a history of ultrasound power over time. 
     
     
       8. The instrument of  claim 1 , further comprising a controller that tracks a temperature. 
     
     
       9. An ophthalmic ultrasound surgical instrument, comprising:
 a surgical hand piece suited for phacoemulsification that includes a phacoemulsification needle that is hollow to define an aspiration passage and that distally terminates at a tip with a tip port, the needle being bent or angled; 
 an infusion sleeve arranged radially outside of the needle so as to define therebetween an irrigation passage to channel irrigation flow, the infusion sleeve defining an irrigation opening arranged for the irrigation flow to exit the irrigation passage; 
 a heat generation reduction structure configured and arranged to reduce heat present at the needle; 
 a horn with a distal section and a resonant section, the distal section being longer than the resonant section, the horn coupled to the needle; and 
 a driver configured and arranged to impart a twisting, rotative movement to the tip at an elevated resonant frequency sufficient to eliminate chatter otherwise present at lower resonant frequencies; 
 wherein the heat generation reduction structure includes a bypass hole in the phacoemulsification needle, the bypass hole being configured and arranged to divert the irrigation flow from the irrigation passage to enter the aspiration passage under suction via the bypass hole while the port is obstructed and thereby prevent the irrigation flow from otherwise exiting through the irrigation opening. 
 
     
     
       10. An ophthalmic ultrasound surgical instrument, comprising:
 a surgical hand piece suited for phacoemulsification that includes a phacoemulsification needle that is hollow to define an aspiration passage and that distally terminates at a tip with a tip port, the needle being bent or angled; 
 an infusion sleeve arranged radially outside of the needle so as to define therebetween an irrigation passage to channel irrigation flow, the infusion sleeve defining an irrigation opening arranged for the irrigation flow to exit the irrigation passage; 
 a heat generation reduction structure configured and arranged to reduce heat present at the needle; 
 a horn with a distal section and a resonant section, the distal section being longer than the resonant section, the horn coupled to the needle; and 
 a driver configured and arranged to impart a twisting, rotative movement to the tip at an elevated resonant frequency sufficient to eliminate chatter otherwise present at lower resonant frequencies; 
 wherein the heat generation reduction structure includes a tubing that is situated between the infusion sleeve and the phacoemulsification needle, the tubing having a texture that is less tacky than that of the infusion sleeve and provides less friction resistance to rubbing action than the infusion sleeve. 
 
     
     
       11. The instrument of  claim 10 , wherein the tubing is made of a polyimide material. 
     
     
       12. The instrument of  claim 10 , further comprising a controller of the driver that directs the driver to alter an amount, duration or type of ultrasound power imparted to the tip of the phacoemulsification needle based on an analysis that tracks a history of the ultrasound power over time and its effect on changing temperature. 
     
     
       13. The instrument of  claim 10 , further comprising a controller of the driver that directs the driver to introduce pauses in the twisting, rotative movement. 
     
     
       14. The instrument of  claim 10 , further comprising a controller of the driver that directs the driver to vary an amplitude of the ultrasound power being applied. 
     
     
       15. The instrument of  claim 10 , wherein the driver is configured to impart the twisting, rotative movement to the tip at a resonant frequency of at least 40 kHz. 
     
     
       16. The instrument of  claim 10 , further comprising a controller of the driver that directs the driver to vary a duty cycle of the ultrasound power being applied. 
     
     
       17. The instrument of  claim 10 , further comprising a controller that tracks a history of ultrasound power over time. 
     
     
       18. The instrument of  claim 10 , further comprising a controller that tracks a temperature.